Familiar faces: "super recognizers" never forget a visage, an unusual ability that can be put to good use.
Carrie Shanafelt is good with faces, too. A professor of literature at Grinnell College in Iowa, Shanafelt can spot her students outside the classroom, whether it's the first week of class or years later. And Ajay Jansari, an information technology specialist in London, often has to see a face only once to remember it, even those he meets thousands of miles from home.
While some people say they never forget a face, these folks have scientific studies to back their claims. Called "super recognizers," they're among a small group of individuals being studied by scientists at Dartmouth College and in England to better understand how some people can recognize almost every face they have ever seen.
Scientists are now putting super recognizers' skills to the test to get a handle on how face-processing areas of the brain work to make a few people so adept at recalling faces. Findings from the studies may advance understanding of how most people categorize faces--a subject that is still poorly understood.
Studies of those with exceptional recognition powers may also influence how police work or other jobs that require identifying people by their faces are carried out. Learning about the variability in people's face-recognition skills may lead to tests for assessing eyewitness testimony, or ways to evaluate individuals seeking jobs in areas like security, where the ability to remember faces may be important. Studies of super recognizers may also reveal ways to help others improve their face recognition abilities.
"By identifying strategies used by super recognizers, we may find ways to train others who have problems with face recognition, or help people who are in the normal range but have professional demands in which superior face recognition-would be beneficial," says Dartmouth psychologist Bradley Duchaine.
Most super recognizers take their powers for granted, or assume that others share their ability to pick a face out of the crowd. Shanafelt says she knew she was good at recognizing others, but wasn't aware there was anything special about her ability until she was tested three years ago.
"Actually, I've always worried about not being able to recognize someone," she says. Her fears, she says now, likely stemmed from the fact that she recognized others far more frequently than they recognized her.
The phenomenon of those who excel at recognizing faces emerged from work on people at the opposite extreme--those who can't recognize faces at all. Duchaine, who studies people on both ends of the spectrum, says that face recognition ability may vary much more than previously thought, running along a spectrum from poor or disordered to exceptional.
"Outside the psychological community, it's something that people likely didn't give much thought to," Duchaine says, because most people assume that "anybody can recognize faces."
What sets super recognizers apart is their ability to remember people they have seen or met only briefly, says Ashok Jansari, a psychologist at the University of East London. Claiming to have "very good, but not super" facial recognition skills himself, Jansari set up an experiment at the London Science Museum to test individuals' facial recognition powers. Of the 730 museum visitors who participated in the studies, seven turned out to be super recognizers. One of them was his brother, Ajay.
To date, only two dozen or so super recognizers have been identified, including a group of London police officers who are extremely good at recognizing criminal suspects. Though studies of super recognizers are just getting under way, findings suggest that about 1 percent of people are super recognizers.
Most people can instantly identify their family members, friends and even foes just by looking at their faces. If your aunt Martha cuts her hair or cousin Joe grows a beard, chances are you'll still know them by their visages. For most, the ability to perceive faces is present from birth. Newborn babies prefer to look at pictures of faces compared with other objects, and a baby as young as 3 days old prefers looking at its mother's face over a stranger's.
"Faces are special," says University of Southern California neuroscientist Irving Biederman, who studies how the brain processes visual information.
"What's unique about faces in terms of our evolutionary history is that it's the only visual stimulus class where we had to make very fine discriminations," he says. "If you see one tiger versus another tiger, you don't really have to make a distinction whether that's Pammy or Tommy. But for human faces, you do."
Though early humans had only a small number of faces to individuate--perhaps only the faces in their own cave- they still had the problem of distinguishing one mug from another, Biederman says. Not only are faces similar in appearance, with two eyes, a nose and mouth, but they change over time: People smile, grimace and frown, and their faces wrinkle with age. Different angles and lighting also influence facial appearance.
"You don't get the exact same image of a face every time you look at it," Biederman says. "Yet, most people recognize the features of those they know, even after gaps of 20 years or more.
"How the brain perceives a face remains a mystery. Some scientists say face recognition is a special type of processing that comes with its own dedicated neural machinery. This mechanism may operate differently from those used for object recognition. Whether face-recognition mechanisms are hardwired or constructed from experience also remains unknown.
Early evidence that the ability to distinguish facial features is localized in the brain came from studies of stroke patients and veterans injured in war. People with damage at the back of the brain on the right side in an area called the ventral occipito-temporal cortex often lost the ability to recognize faces.
Such studies gave scientists reason to think that there could be a special region in that vicinity of the brain dedicated to face recognition.
By the late 1990s, researchers were turning to functional magnetic resonance imaging, or fMRI, to get more precise information. By monitoring the blood flow in different regions of the brain as subjects viewed faces and other objects, scientists could see which brain areas are most active.
In 1997 Nancy Kanwisher, now of MIT, and her colleagues used fMRI to pinpoint an area that appeared to be specialized for detecting faces. This brain area, called the fusiform face area, would light up with activity when subjects viewed faces, but showed less activity when subjects viewed other objects such as houses. Still, the studies couldn't tell whether this region was actually required to recognize the face it was seeing.
"Just because you see some part of the brain turn on when you look at faces, it doesn't mean that it's necessary for face recognition," Kanwisher says.
Recently, scientists got more direct confirmation. Kanwisher's group, along with others, ran experiments using a noninvasive technique known as transcranial magnetic stimulation, or TMS, to interfere with brain activity near the fusiform face area while subjects were viewing faces. The scientists also tested to see what happened in this region when subjects viewed other body parts. TMS works by inducing weak electric currents in the neurons in a selected brain region, causing a temporary interference with normal activity. In this case, the scientists targeted the right occipital face area, located next to the fusiform face area. By messing up the recognition process in this manner, Kanwisher's group confirmed prior findings that zapping this region interferes with face recognition.
How much of the face-recognition process happens within this region remains unknown, Kanwisher says. Beyond this area, scientists are working to figure out what other brain structures are required for processing faces.
"There must be some other brain regions" involved, Kanwisher says, noting that the fusiform face area on its own probably can't house a conscious experience of a face. "For that it most likely must talk to lots of other brain areas."
Scientists curious about how the brain works to make a positive identification have often studied those who have a tough time recognizing faces. Stroke victims or those with autism may have such problems. Another group includes those with an affliction called face blindness, or prosopagnosia. People with this condition may find it nearly impossible to identify their spouses or family members, yet most can easily pick out differences in objects such as cars, tools or landscapes.
Some develop the condition after suffering a stroke or brain injury. Others --about 2 percent of the general population--are born with face blindness. It was from such studies that scientists discovered that some people actually excel at face recognition.
Duchaine, who has studied face blindness for 15 years, says he and his colleagues would hear people say, "I'm not face blind, I'm the opposite."
"We finally decided to look into it," he says.
Working with Richard Russell, now of Gettysburg College in Pennsylvania, and Harvard psychologist Ken Nakayama, Duchaine published the first report on super recognizers in 2009. These initial findings, published in Psychonomic Bulletin & Review, suggested that people with this ability might actually look at faces differently than others do.
Getting the whole story
Super recognizers excel at discriminating among the countless faces they encounter. But faces change over time. People switch hairstyles or glasses, or suddenly shave. Super recognizers are able to see through changes in appearance to recognize near strangers whom they have not seen for years.
Case in point: Two years after visiting a theme park in Florida, Jansari's brother Ajay ran into the woman who had served as a tour guide. Though she now worked as a clerk in a kitchenware store, he immediately recognized her.
How did he do it? One possibility, scientists say, is that super recognizers' brains are better than others at something called "holistic" processing, or viewing the face as a single unit. Studies of those with face blindness show that people who have difficulty recognizing faces tend to focus on individual parts. By contrast, people with normal face-recognition ability process faces as a "whole." Duchaine says that super recognizers maybe able do this kind of processing even better than others, "though this possibility remains to be tested."
His group and Jansari's are now independently looking to see if there's a difference in the way super recognizers process faces. To isolate holistic processing mechanisms, the researchers are using various face-recognition tests, including one called composite-face effect. In this test, images of faces are split horizontally so that there's a top half and lower half. Researchers then align the top half of one face with the lower halves of several others.
When scientists ask subjects "Are the top halves of those faces the same?" people have a hard time seeing that the two halves are the same because their brain automatically fuses the top and lower halves to form a new, unfamiliar face, Duchaine says. The more you rely on holistic processing, the harder the task is.
Though researchers don't yet have data on super recognizers' performance at this task, Duchaine anticipates that they may not score highly if they're using a holistic approach to look at faces.
Another test of holistic face processing is the whole-part effect: Here, subjects are shown an unfamiliar face, then asked to identify individual features by looking at images of various eyes, noses or mouths. Most people do better when a feature is presented within the whole face than when it stands on its own, Duchaine says.
"Eyes, and other features, are influenced by rest of the face," he says. "If the rest of the face isn't there, it's more difficult to tell whether a particular pair of eyes are the same because you're viewing them in a slightly different manner."
Scientists are also looking to see if super recognizers have other exceptional powers, such as superior perception, which is the ability to tell one unfamiliar face from another simultaneously presented face. Such powers might aid or work in addition to recognition, which is remembering a previously seen face.
Joe DeGutis, a fellow at the Harvard Vision Sciences Lab who studies those with face blindness, refers to perception as a "front-end procedure" that allows one to take in visual information about a face and encode it. This skill is routinely used by security agents to match faces on a screen or compare an ID photo against the face of the person presenting it.
Facing up to the task
Police officers also may draw upon perceptional ability to ID suspects. Josh P. Davis, a psychologist at the University of Greenwich in London, is studying a group of police officers in London to see how perceptional ability aids in recognizing faces pulled from closed-circuit camera images. Davis began studying the officers for super recognition abilities after hearing of their near-superhuman perception abilities to match faces from such images.
Only months after setting up his program to study the officers, riots broke out across London. A core group of 20 officers were able to ID more than 600 suspects from grainy and incomplete images collected by security cameras. One officer alone accounted for 190 identifications, pulling from memory faces he had seen before. In many cases, rioters wore heavy disguises--using scarves, bandannas, and hooded sweatshirts to protect their identities--leaving only the eyes visible.
Tests of the 20 officers confirmed at least five are super recognizers, Davis says. The others scored above control subjects on the test. As a result of the study, the police department has changed its system, giving super-recognizer officers extra time to view images distributed throughout the department.
"If you've never seen someone before, you're not going to recognize them, no matter how good your face-recognition skills are," Davis says. "But super recognizers seem to be able to remember far more faces they've encountered than the rest of us, and to learn new faces far more efficiently."
Davis has teamed up with Jansari to better understand how super recognizers make these associations, and to see if they're related to perception as well as recognition. Writing in an upcoming issue of Psychologist, the scientists say super recognizers may be extra efficient at extracting information about a face, especially if viewed in action. Davis says that previous studies have shown that people can extract more information about a face if it's moving, as opposed to looking at a still image. But he says the police officer super recognizers seem to have a disproportionate advantage over others for gleaning information about faces as they scan video images or watch people in motion.
This summer, he began probing the officers' perceptional abilities, using souped-up versions of standard face recognition tests to see how well these super recognizers discriminate between similar faces. He's also running a battery of tests to see if the officers are better than control subjects at feature-by-feature matching.
"A lot of the officers claim that their abilities are down to recognizing specific facial features, or idiosyncratic features such as a tattoo or scar," Davis says. He wants to see whether the police officers are right about their abilities, or if they view faces in the same holistic manner that seems to drive most people's face-recognition process.
Though face recognition may not automatically improve with use, some studies suggest it's a skill that can be honed to some degree. Psychologist Isabel Gauthier of Vanderbilt University in Nashville has shown that the face-processing areas of the brain can be trained to identify other objects, such as cars and birds, holistically. Her findings suggest that if bird-watchers and car buffs can train their brains to specialize, others can, too.
Duchaine wants to identify the strategies used by super recognizers to help those with problems identifying faces. Such strategies might also boost performance among those working jobs that require checking photo IDs. In the future, customs and border patrol agents, as well as TSA agents working in airports, might be tested for their facial recognition abilities and put to work where their ability to super recognize is more than just a curiosity.
Meanwhile, just knowing that face recognition ability runs along a spectrum--with some being exceptional--may give pause to criminals or others looking for mischief.
"If I were going to commit some criminal act," Davis says, "I might be deterred by the fact that there might be somebody recognizing me, or who later might see an image of me committing that act."
1 out of 100
People classified as super recognizers
Caption: Find that face: Super recognizers are better than average at matching a target face (left) to one of the six shape-adjusted faces on the right. When a similar test is conducted by adjusting the pigmentation of faces, super recognizers still outperform people with average face-recognition ability. This suggests that the face-recognition process in super recognizers integrates information about shape and pigmentation.
SOURCE: R. RUSSELL ET AL/ NEUROPSYCHOLOGIA 2012
Caption: Match game Face-matching tasks show that people are good at recognizing faces as a whole but struggle to identify mismatched features or those shown in isolation. Test 1 (left) shows that it's easier to match faces when the images are right-side up rather than upside-down. Test 2 (center) shows that it's easier to tell if two halves of a face belong to the same person when the halves are offset rather than aligned. Test 3 (right) shows it's easier to make a match based on whole faces rather than eyes alone. SOURCE: J. DEGUTIS ETAL/COGNITIVE NEUROPSYCHOLOGY 2012
Caption: One London police officer with exceptional recognition powers spotted and arrested a suspect on a busy street 18 months after seeing video of the man committing an armed robbery.
Please note: Illustration(s) are not available due to copyright restrictions.
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|Date:||Sep 7, 2013|
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